Pulse and γ-radiolysis of concentrated perchloric acid solutions

Abstract

Pulse and γ-radiolysis of concentrated perchloric acid solutions has been investigated. Since perchlorate ion is unreactive to the water decomposition products such as e_eq^–, H and OH, solute decomposition occurs only through the direct effect of radiation. From pulse radiolysis experiments using scavengers, G(ClO₄˙)= 0.083 ± 0.01 and G(ClO₃˙)= 0.052 ± 0.01 µmol J^–1 have been determined. In highly concentrated solutions, two components with transient absorption at 350 and 440 nm are observed. The shorter-wavelength component is attributed to ClO₃˙. G(ClO₃˙) calculated using ε= 470 m² mol^–1 at the peak is 0.052 µmol J^–1, which is consistent with the value determined from scavenger experiments. The longer-wavelength component is detected in perchloric acid solutions with concentration > 10 mol dm^–3. This species is tentatively assigned to HClO₄⁺, formed in the direct decomposition of HClO₄ molecule. From γ-radiolysis G(ClO₃^–)= 0.10 ± 0.01 µmol J^–1 was determined, and O(³P) is formed together with ClO₃^–. With G(ClO₄˙)= 0.083, G(ClO₃˙)= 0.052 and G(ClO₃^–)= 0.10 µmol J^–1 and the reaction scheme proposed in this work, the yields of the final products reported previously can be explained.